This invention relates to lamps and more particularly to such lamps employing an outer envelope surrounding a light source capsule. The light source capsule can be an arc discharge source or a halogen incandescent source, both of which operate at very high temperatures and both of which may continue to operate in the event that the outer envelope breaks. In the case of an arc discharge source this breakage can expose outlying areas to potentially dangerous ultraviolet radiation and in the case of a halogen incandescent source, which is more likely to used in a home environment, can leave the very hot capsule exposed.
These problems have long been recognized in arc discharge lamps and safety features for extinguishing the capsule in the event of outer envelope breakage are available. Usually, this feature comprises an incandescent filament in series with one of the in-leads of the lamp. Since the outer envelope is evacuated the filament can even be used to add to the light output of the lamp by incandescing during operation. However, in the event of breakage of the outer envelope, the continuously burning filament is exposed to the oxygen of the air and virtually immediately burns through, opening the circuit and extinguishing the capsule. This solution works well in the relatively expensive arc discharge lamps and, relatively, adds little to the cost. Such a solution, however, would be expensive for the much less costly halogen incandescent lamps, which are normally used in the home environment.
It is, therefore, an object of this invention to obviate the disadvantages of the prior art.
It is another object of the invention to provide an economical shut-off feature for halogen incandescent lamps.
Yet another object of the invention is the enhancement of lamps employing light source capsules.
Still another object of the invention is the provision of a combination mechanical and electrical termination of a light source capsule used in an outer envelope in the event of outer envelope breakage.
These objects are accomplished, in one aspect of the invention, by mounting a safety switch in a lamp having an outer envelope with a light source capsule mounted therein. The lamp has a base for connection to an electrical circuit via a mating socket and has in-leads appropriately connected to the base and to the light source capsule whereby electrical power can be supplied to the light source. A fuse is operatively mounted to one of the in-leads in the base. The safety switch is mounted in the outer envelope and tensioned thereagainst whereby breakage of the outer envelope causes the safety switch to release and electrically contact the in-leads causing a short circuit and opening the fuse, thereby removing power from the capsule.
This combination mechanical-electrical safety switch is economical to manufacture and install and insures the deactivation of the light source capsule in the event of outer envelope breakage.